Expression used by cyclists to describe excercise induced low
blood sugar levels; being a feeling of light-headedness and
weakness in all
limbs. Similar to 'The Wall' in running. Has fallen out of usage in recent years due to alternative meanings.
I am feeling a bit light-headed, if I don't have
a banana, I think I'm going to bonk.
I've got
the bonk.
I
bonked really badly and had to get a lift home.